This invention relates to a color sensor.
A color sensor using a single crystalline silicon and amorphous slicon (a-Si) is known in the art. For example, a color sensor using a-Si is disclosed in Japanese Laid-Open Publication (KOKAI) Nos. 58-106863, 58-31585, 58-12585, 58-12586, 58-12587, 58-12588 and 58-12589.
However, the conventional color sensor necessarily requires red, green and blue color filters, providing a cause for high costs. In order to split an incident light beam containing color components of various wavelengths into red, green and blue color components (the three primaries of light), three photosensing areas at most need to be arranged in a planar array, serving to impede enhancement of image resolution.
As a solution to this problem, for example, Japanese Laid-Open Publication (KOKAI) Nos. 58-4143 and 59-4184, for example, disclose a color sensor having photosensing areas which are stacked one over another. This color sensor is adapted to sense the incident light color in accordance with a ratio of the magnitudes of photocurrents in the photosensing areas.
However, this method is only effective on an incident monochromatic light beam, and it has been difficult to identify the various color components into which the incident light beam containing various color components is separated. Furthermore, this color sensing method is complex, because, subsequent to the sensing of the ratio of photocurrents, a color corresponding to this ratio must be evaluated.